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(last updated: Jan. 17, 2013)

Page Contents:

  1. Overview
  2. Description of Study Areas
  3. Experiments
  4. References


In ALMIP Phase 2, LSMs will be evaluated using observa- tional data from three heavily instrumented supersites from the AMMA-Couplage de l'Atmosphère Tropicale et du Cycle Hydrologique (CATCH) observing system (Mali, Niger, and Bénin) (see figure below). The AMMA-CATCH window covers a north-south transect encompassing a large eco-climatic gradient (
Lebel et al., 2009). Mesoscale simulations will be performed and analyzed for the three mesoscale squares (located within Mali, Benin and Niger) The spatial resolution of the 3 mesoscale grids is 0.05 degrees, and the temporal forcing uses a 30 minute time step. The local scale data sites are located within the three meso-scale intensive measurement zones.

Fig. 1. The ALMIP (Phase 1) regional scale domain is shown. The sub-regional (mesoscale: violet outline) and rectangles containing local sites are shown: Oueme (red), Niamey (orange), and Gourma (blue). The ECOCLIMAP annual average LAI (m2 m-2) is contoured.

Description of Study Areas

Benin meso-square

    The Ouémé-Benin site (9oN­10.2oN; Guyot et al., 2009) has annual rainfall which averages between 1200­1300 mm. The vegetation is wooded savannah with interspersed crops in- cluding maize and niébé. Simulations will focus on the upper Ouémé watershed (14,600 km2). There will also be a focus at a higher resolution over the densely instrumented Donga catchment (which is a part of the the Oueme basin: Seguis et al., 2011). The rainy season lasts from April to October. Contrary to the two other Sahelian sites, river runoff is structured by an arborescent drainage network, and sustained by the drainage of water-tables. The vegetation cover is patchier than on the other sites, with forest clumps scattered in mixed fields and fallow landscape.

Niger meso-square

    The South-West Niger site (13oN­14oN) is typical of the central Sahel conditions with average annual rainfall decreasing from 570 mm in the south to 470 mm in the north (1990­2007 average). The mesoscale site is located near Niamey, generating heavy demographic pressure, including intensive agricultural usage and wood cutting for fuel. The area is now essentially composed of millet fields, fallows, and tiger bush (Cappelaere et al., 2009). Simulations will be performed for a 1-degree square (2-3oE; 13­14oN) characterized by a typical semi-arid tropical climate with a long dry season (from October to May) followed by a wet season of 4 to 5 months.

Mali meso-square

    The Gourma-Mali site located in the northern Sahel (14.8oN­ 17.3oN) is a typical rangeland region, covered with semi-arid natural vegetation. LSM simulations will be focused on the Hombori super site, a 50 x 50 km area which extends over the central Sahel where most of the in situ instrumentation is concentrated (Mougin et al., 2009). The rainy season is short, lasting from late June to mid-September, with an average annu- al precipitation recorded at Hombori over 1950­2007 of 370 mm. The site is characterized by three soil types over which two different hydrologic systems operate. Vegetation comprises a herbaceous layer almost exclusively composed of annual plants, among which grasses dominate, and scattered bushes, shrubs, and low trees.

Description of Experiments

    Two main experiments will be performed, and they are differentiated by the spatial scale. The first experiment will be at the mesoscale using a grid resolution of 0.05 degrees, and covering several years during and after the Enhanced Observation Period (EOP: 2005-2008) and en- compassing the Special Observation Period (SOP: 2006). Participants will be requested to run their models for the prescribed time period (which is a function of the site) for the three mesoscale squares using two different atmospheric forcing input datasets (which only differ in terms of the rainfall for the control experiments). Hydrological models will perform this experiment for the Benin domain only (Ouémé and the Donga sub-basin) where extensive hydrological measurements have been taken. The second set of experiments will be performed at the local scale during the same time period for several representative sites within each of the mesoscale "squares". The addition of more optional experiments is possible if the time to do the runs and the required input data stay reasonable.

Note that as of early 2013, the Donga experiment has been put on hold (it is optional).

We also request that modelers repeat the control experiments using the updated ECOCLIMAP2-v2 data, which extends to 2008. Note, this is not applicable to models simulating the vegetation: for such models, they will provide one set of control experiments from 2005-2008 (using both precipitation puts). A summary of the Control and Optional mesoscale experiments is given below. Note that we strongly recommend the optional experiments. More optional experiments might be discussed during the ALMIP2 Workshop. A summary of the local scale experiments is forthcoming.

Site Time Period Precip Forcing Input ECOCLIMAP data Notes
Niger 2005-2007 Lagrangian ECOCLIMAP2 (default) Control Exp
Niger 2005-2007 Thiessen ECOCLIMAP2 (default) Control Exp
Benin (Oueme) 2005-2007 Lagrangian ECOCLIMAP2 (default) Control Exp
Benin (Oueme) 2005-2007 Thiessen ECOCLIMAP2 (default) Control Exp
Mali 2006-2007 Thiessen ECOCLIMAP2 (default) Control Exp
Niger 2005-2008 Lagrangian ECOCLIMAP2-v2 Optional
Niger 2005-2008 Thiessen ECOCLIMAP2-v2 Optional
Benin (Oueme) 2005-2008 Lagrangian ECOCLIMAP2-v2 Optional
Benin (Oueme) 2005-2008 Thiessen ECOCLIMAP2-v2 Optional
Mali 2008 Lagrangian ECOCLIMAP2-v2 Optional, *
Mali 2006-2008 Thiessen ECOCLIMAP2-v2 Optional
Mali 2008 Lagrangian ECOCLIMAP2-v2 + Alternate soil parameters Optional, **
Mali 2006-2008 Thiessen ECOCLIMAP2-v2 + Alternate soil parameters Optional

* Please initialize the Mali Lagrangian ECOCLIMAP2-v2 experiment on Jan 1. 2008 using the last time step from your Mali Thiessen ECOCLIMAP2-v2 run (Dec 31, 24h, 2007).

** Please initialize the Mali Lagrangian ECOCLIMAP2-v2 Alternate-soil-parameter experiment on Jan 1. 2008 using the last time step from your Mali Thiessen ECOCLIMAP2-v2 Alternate-soil-parameter run (Dec 31, 24h, 2007).

Please refer to the Experiment Overview (and instructions) document for details regarding the experiments, analysis etc. See and for a summary of the forcing data.


Cappelaere, B., et al., 2009. The AMMA-CATCH experiment in the Sa- helian area of south-west Niger ­ Investigating water cycle response to a fluctuating climate and changing environment. J. Hydro, 375, 34­51.

Guyot, A., J.-M. Cohard, S. Anquetin, S., and C. R. Lloyd, 2009. Com- bined analysis of energy and water balances to estimate latent heat flux of a Sudanian small catchment. J. Hydro, 375, 227­240.

Lebel, T., et al., 2009. AMMA-CATCH studies in the Sahelian region of West Africa: An overview. J. Hydro., 375, 3­13.

Mougin, E., et al., 2009. The AMMA-CATCH Gourma observatory site in Mali: Relating climatic variations to changes in vegetation, surface hydrology, fluxes and natural resources. J. Hydro, 375, 14­33.

Séguis M., Kamagaté B., Favreau G., Descloitres M., Seidel J.L., Galle S., Peugeot C., Gosset M., Le Barbé L., Malinur F., Van Exter S., Arjounin M., Wubda M., 2011. Origins of streamflow in a crystalline basement catchment in the sub-humid Soudanian zone : the Donga basin (Benin, West Africa). Inter annual variability of water budget. J. Hydro, 402, 1-13, doi: 10.1016/j.jhydrol.2011.01.054

Note that most of the pertinent information on the experiment can be found in the overview document.